The ganzfeld electroretinogram has revealed that both dopaminergic blockers and GABA potentiators have an inhibitory effect on human rods and cones. In a related clinical study, we have repeatedly shown the blue-sensitive cone system to be altered in male drug-free patients with schizophrenia when compared with age- and sex-matched controls. These results suggest that the neuromodulators of the retina may be altered by psychoactive drugs and psychiatric disease in a manner similar to less accessible CNS structures.